1. Field of the Invention
This invention relates to a dielectric article suitable to be used in dielectric parts of condensers (capacitors), semiconductor devices, light emitting devices, etc.
2. Related Background Art
Materials used for forming dielectric parts of condensers, semiconductor devices, light emitting devices, etc. are required to have a high permittivity. As these dielectric materials, ceramics have been mainly used.
Ceramics have a multi-component type structure formed from a plurality of inorganic materials through a calcination step and have the maximum point of permittivity (.epsilon.) in the vicinity of the phase transition temperature Tc as shown in FIG. 6 and they function as dielectric when used in such a state that they can exhibit a high permittivity at the phase transition temperature Tc or in the vicinity thereof.
Ceramics as dielectric materials generally contain additives called shifter or depressor in order that they can have sufficiently high permittivity in the range of temperatures at which the articles in which they are incorporated are used, for example, room temperature or in order to extend the temperature range where high permittivity is obtained, namely, to extend the temperature range where they can be used as dielectrics. The shifter is added to shift the phase transition temperature Tc and the depressor is added to change the pattern of temperature characteristics of permittivity at phase transition temperature Tc or in the vicinity thereof.
Conventional dielectric articles comprising ceramics have the following problems:
(a) There are limitations in the scope in which phase transition temperature Tc can be shifted and in the scope of maximum value of permittivity which can be controlled.
(b) Addition of shifter or depressor causes reduction of permittivity or makes preparation or calcination procedure of raw materials complicated.
(c) The ceramics have multi-component structure and hence are difficult to form as a single crystal film or oriented film.
(d) Dielectric loss is apt to increase or defects such as pin holes are apt to occur and characteristics of the article per se cannot sufficiently be utilized.
Thus, the conventional dielectric articles have not necessarily sufficiently met the requirements demanded as dielectric articles while they are now applied for a wide variety of uses.